1. Field of the Invention
This invention relates to a method and apparatus for automatically removing the shells of boiled hens' or quails' eggs without injury to the albumen.
2. Description of the Prior Art
Heretofore, a strong demand has been placed on automating the peeling of boiled eggs because especially in restaurants and hospitals, where a large quantity of boiled eggs are consumed, peeling of boiled eggs by manual operation would not be efficient economically. Various proposals have been made so far to meet this demand.
As one of such solutions, it is known to use a rotating tube of hexagonal cross-section or circular cross-section with inner projections into which the boiled eggs are introduced and repeatedly raised and dropped for crushing the shells and separating them from the boiled egg contents. This method has a drawback that the egg shells and shell membrane are broken simultaneously from the outset under a strong force of impact, resulting in an injury to the surface of albumen and a number of rejects. Moreover, part of the broken egg shells may remain on the resulting boiled egg contents, thus necessitating post treatment such as washing with water.
There is also known a method wherein the boiled egg is held by several bars or rods and thereby pressed repeatedly for forming numerous cracks on the shell. The respiratory cell portion of the egg is then broken by a hammer and then water is injected through the cells for floating the remaining shell from the albumen. Thereafter, a resilient member such as a rubber member is pressed against the broken respiratory cell portion of the egg shell, and the boiled egg is pressed on the opposite side for removing the shell from the boiled egg contents. However, this method involves a batch-wise operation and, moreover, manual operation as required in setting the boiled eggs on a device for breaking the respiratory cell portion, thus requiring considerable working hours. In addition, there is the risk that the albumen may be injured during breaking the shell at the respiratory cell portion, thus making it difficult to perform the peeling of a great number of eggs in a short time.
It is also known to pinch the boiled egg between a pair of friction rolls for forming cracks on the shell and then to supply the egg into a water vat for allowing the water to be intruded into a space between the albumen and the shell membrane. Then, the egg is conveyed by a bucket conveyor into a space between a pair of rubber rolls for peeling the shell under the effect of a pressing force and the friction between the rolls. This method is superior to the above two methods in that it provides a fully automated peeling operation, however, there is still the risk that the albumen may be injured because the shell membrane may be broken simultaneously with breaking of the shell.